I found a site tonight expending great effort to create art in many forms with coffee.

The person featured claims to have discovered coffee as a film developer.

There is some interesting discussion of instant vs brewed, coffee acidity and alkali, as well as some gelatin he is selling and recipes for homebrew silver chloride paper.

No recipes per se, but interesting. You have to dig a little.

http://www.costaricacoffeeart.com/index.php